Dynamic assignment of Home Address (HoA) and Home Agent (HA) for a mobile station is more than just a desirable or recommended feature for mobile wireless packet data networks. Leading wireless service providers and/or operators have recognized dynamic HoA and HA assignment as a fundamental requirement for their CDMA2000 networks and have emphasized this in multiple conferences world-wide. This has led industry standard organizations like the Internet Engineering Task Force (IETF) and the 3rd Generation Partnership Project 2 (3GPP2) to include requirements for dynamic HoA and HA assignment in several of their standards.
While the working mode between the wireless packet data network and the mobile station is well-defined by various standards, the Remote Authentication Dial-In User Service (RADIUS) extension for dynamic HA selection algorithm has not been discussed or defined clearly anywhere. For example, the document CDMA2000 WIRELESS IP NETWORK STANDARD: SIMPLE IP AND MOBILE IP SERVICES, published by the Code Division Multiple Access (CDMA) mobile network standard body 3GPP2, states the following, “The Home RADIUS server shall implement an HA selection algorithm to perform dynamic HA assignment. The implementation details of this algorithm are outside the scope of this document.”
To make the Dynamic HA (DHA) assignment an effective and efficient function in networks, an HA selection algorithm can be developed and supported by relevant network elements. Current selection algorithms lack intelligence and do not offer a comprehensive DHA solution. Also, they do not proceed further to explore the potential from both the network and mobile station perspective.
Current HA selection methods in the mobile wireless market today allow the home RADIUS Authentication, Authorization, and Accounting (AAA) server to choose a HA from a predefined subset of HAs, such as an HA group, using a traditional Round Robin (RR) approach, with no proper knowledge of the actual working condition of the HA. Some modified selection methods use an HA monitoring functionality that uses standard protocols, such as Simple Network Management Protocol (SNMP) and RADIUS to monitor the HA operational status that are used to solely trigger predefined HA overload policies on the AAA server. The HA can be configured to send traps to the AAA server upon hitting a defined threshold (e.g. overload), or the AAA server can proactively poll the HA for status information. If the AAA server detects that a particular HA is overloaded, it marks that HA as “unhealthy” and starts to either skip requests to the HA (i.e. instead of performing a 1:1 traditional RR between the two HAs in the group, it now does a 1:N RR where N is configurable on the AAA server), or locks out the HA for a configurable period of time (in cases of extreme overload).
All current HA selection methods do not actually avoid an overload condition on the HA, but rather try to deal with it when it happens. RR, if not properly used, may lead to decreasing the HA geographic redundancy level in the network. For instance, if a network had three HAs with one HA′ capacity significantly higher than the others, then performing an RR selection will fill-up the capacities of the two smaller HAs and leave the system running with the one larger capacity HA. Another critical problem with current HA selection methods is that the methods do not provide a reasonable balance between delay mitigation, by giving preference to HAs based on geographic proximity, and the current HA load.
For the reasons discussed above, a solution is needed that performs dynamic HA assignment in an intelligent manner so as to take into consideration problematic HAs such as those in an overload or potential overload condition, and takes into consideration other factors such as geographic location and capacities of HAs. The solution should be integrated with the existing RADIUS/AAA infrastructure.